There is a gamut mapping technique that represents a color, which exists in a color space (e.g., an RGB color space of a digital camera) with a broad color gamut but does not exist in a color space (e.g., a CMYK color space of a printer) with a narrow color gamut, in the color space with the narrow color gamut. The general gamut mapping attains the above color representation by selecting a region where it seems like an identical color (e.g., by selecting an equal hue line, selecting a region where it seems like an identical color, and so forth), as disclosed in, e.g., Japanese Patent Laid-Open No. 2004-104604.
The color of red is reproduced by a combination of color recording materials of magenta and yellow. The color of magenta using the color recording material of magenta has characteristics L*≈45, a*≈82, and b*≈2 on an L*a*b* color space. The color of yellow using the color recording material of yellow has characteristics L*≈88, a*≈4, and b*≈105 on the L*a*b* color space. The color of red is reproduced using these two color recording materials.
However, new ink as a color recording material of magenta is developed (to be referred to as “new magenta ink” hereinafter), and the color of magenta using the new magenta ink has characteristics L*≈41, a*≈82, and b*≈24 on the L*a*b* color space. Therefore, the differences from the conventional magenta ink (to be referred to as “old magenta ink” hereinafter) are ΔL*≈4, Δa*≈0, and Δb*≈26, i.e., the lightness value is low, and b* assumes a very small value.
Note that new ink as a color recording material of yellow is also developed (to be referred to as “new yellow ink” hereinafter), and its characteristics (color) are nearly the same as those of the conventional yellow ink (to be referred to as “old yellow ink” hereinafter).
When the color of red is reproduced using the new magenta ink and new yellow ink with these characteristics, its lightness and saturation values are low, and subdued red is reproduced, i.e., a visually favorable color cannot be obtained. Hence, how to reproduce the visually favorable color of red is a question. As described in Japanese Patent Laid-Open No. 2004-104604 above, if an equal hue line is used, a close visual hue value can be selected on the color space with the narrow color gamut, but a saturation value often becomes low. In this case, a color with a subdued, light impression is obtained. If this is used in the reproduction of a photo or the like, a color that creates an impression different from that in the original photo is reproduced.
Furthermore, no problem is experienced when an allowable range of an identical color exists. However, when the color gamut is different beyond the allowable range, no measure can be taken.